Design of Optical Micromachines for Use in Biologically Relevant Environments

Abstract

Advances in nanofabrication over the past twenty years have enabled the creation and use of ever-more interesting and useful micromachines. Optical micromachines are a particularly attractive subset of these for researchers in biological and soft-matter sciences, due to their potential to aid in optical tweezer studies of laser-sensitive samples. However, the development of multi-component micromachines is made difficult due to the dominance of surface forces at this scale, which is made all the more relevant in the high-salt concentrations used for biological studies. This study concerns the design of simple, first-class lever micromachines for use in environments with different salt concentrations, in an attempt to provide a guideline for design requirements of functional optical micromachines for use in physiological conditions.

Developing an Optical Microlever for Stable and Unsupported Force Amplification

“…While this is an extremely simple concept, the prevalence of surface forces contributing to adhesion at the microscale means that even ensuring the lever will rotate is a relatively difficult task. Attractive forces on the microscale are associated with small separation distance and large overlapping area between objects, so introducing large gaps between parts, and minimising the overlapping area both seem like appropriate first steps when creating functional micromachines [28], [29]. However, in this case, the goal is to demonstrate effective multiplication of force, which requires some contact between the pin and the lever arm.…”

“…The choice to use a small lateral gap contrasts with our earlier work [29], where a gap of 1.6 µm was used, in order to increase the chances of rotation in high ionic strength environments. However, in that work the primary motivator for such a large gap was to decrease the overlapping area between the pin and the lever arm.…”